Self-shine emulsions for floors have been in use for many years both in the home and in factories and offices. There has been no shortage of attempts to use these products for other purposes, for example for treating shoes.
However, whereas floor coverings (plastic, wood or stone) are essentially non-deformable, inelastic materials which do not undergo any deformation, even under foot, leather is a deformable, stretchable, elastic and supple material which, when worn in the form of shoe uppers, is required to show all these properties which are specific to leather. Added to this is the fact that shoe-care preparations are generally applied daily or after each wearing, whereas self-shine emulsions for floors are normally only applied at intervals of 1 to 6 months. These differences between floor coverings and leather make it easy to understand why the requirements which a product for floors and a shoe- and leather-care preparation have to satisfy are totally different. Attempts to use products developed for treating floors as shoe- and leather-care preparations have failed for the following reasons:
1. On leather, self-shine emulsions for floors lead to breakage and separation of the film from the shoe upper leather due to the inadequate elasticity and flexibility of the film.
2. Even after a few applications, self-shine emulsions for floors build up thick films, resulting in the formation of coatings on the shoe upper leather; in masking of the natural grain of the leather; in crust formation; and in loss of the breathing ability of the leather.
3. Because of pH-values of 9 and higher, self-shine emulsions developed for floors cause embrittlement of, and attack on, the leather, causing it to crack.
4. Conventional self-shine emulsions do not properly care for leather nor keep it soft; they also impair its elasticity.
These findings are also confirmed by tests on various leather surfaces conducted with products and inventions in the field of self-shine floor cleaning preparations; see for example German Application No. 17 69 467, French Patent No. 2,332,312 and East German Patent No. 104,316.
It was only recently that successful attempts were made, by combining selected quantities of certain active substances, to develop self-shine emulsions of the type which could also be used for shoe and leather care (European Patent Applications No. 17 119, and No. 36 956). Such self-shine emulsions are distinguished by their ability to form elastic and deformable films which withstand the severe deformation and flexing encountered in leather wear and which, at the same time, provide the leather with a high shine without any need for polishing. By virtue of their favorable performance properties, products of this type have found an established place in the shoe-care market although they are mainly limited in their application to smooth, heavily covered leather.
This limitation emanates in particular from the fact that, when treated with preparations of the type in question, natural leather, leather finished with a silk - like sheen or leather deliberately kept dull readily undergoes a change in its surface character through excessive gloss build up and also from the observation that light, pastel-colored, and uncovered or substantially uncovered leather often darkens or becomes patchy, a disadvantage which is mainly attributable to the considerable content of low-boiling solvents in those compositions. The disadvantages referred to cannot be obviated simply by changes to the formulations of the compositions, such as reducing their solids content and the quantitites of solvent present. On the contrary, changes such as these produce deteriorations in other properties, such as the flexibility of the film.